Ionization and dissociation of acetonitrile by intense femtosecond laser pulse

Photoionization and photodissociation of CH3CN were studied by a linear time of flight mass spectrometer coupled with 800 nm, 50 fs laser pulses at intensities of 6.3×1013-1.2×1014 W/cm2. The laser power dependences for principal ions CH3CN+, CH2CN+, CHCN+ and CCN+ were measured, which are consistent with the numbers of photons required to produce the ions via multiphoton ionization and dissociation. The results show that eight-photon non-resonant multiphoton ionization is the main photoionization mechanism of the parent ion CH3CN+, while the fragment ions were produced through the dissociation of the molecules in the super-excited states.